The present invention relates to mufflers for motor vehicles and, more particularly, to a twin muffler, which has two muffling units arranged in parallel for softening sound of engine exhaust gas efficiently.
A regular muffler for a motor vehicle exhaust pipe, as shown in FIG. 1 , is generally comprised of a cylindrical casing, a perforated inner tube axially mounted in the cylindrical casing, and a formed material stuffed in the cylindrical casing around the perforated inner tube. This structure of muffler cannot effectively soften sound produced by striking of exhaust gas against the peripheral wall of the cylindrical casing. Further, this structure of muffler gives little help to the improvement of the output torque of the engine.
The invention provides a twin muffler, which eliminates the aforesaid drawbacks. According to one aspect of the present invention, two muffling units are connected in parallel to a manifold adapted to receive engine exhaust gas. Each muffling unit comprises a front accumulation chamber, a rear accumulation chamber, a perforated inner tube connected between the accumulation chambers, a tapered guide tube adapted to guide exhaust gas from the perforated inner tube to the rear accumulation chamber, a foamed material stuffed between the accumulation chambers around the perforated inner tube, and an exhaust endpiece adapted to guide exhaust gas out of the rear accumulation chamber. The perforated inner tube has a twisted middle section, which causes exhaust gas to form a spiral flow. The front accumulation chamber buffers the velocity of intake flow of exhaust gas, so that less noise is produced when exhaust gas passing through each muffling unit.